Add data usage collect with its new admin API (#8553)

Admin data usage info API returns the following

(Only FS & XL, for now)

- Number of buckets
- Number of objects
- The total size of objects
- Objects histogram
- Bucket sizes

cmd/posix-diskid-check.go

@@ -38,6 +38,10 @@ func (p *posixDiskIDCheck) IsOnline() bool {
 	return storedDiskID == p.diskID
 }
 
+func (p *posixDiskIDCheck) CrawlAndGetDataUsage(endCh <-chan struct{}) (DataUsageInfo, error) {
+	return p.storage.CrawlAndGetDataUsage(endCh)
+}
+
 func (p *posixDiskIDCheck) LastError() error {
 	return p.storage.LastError()
 }